1. Field
The disclosed concept relates generally to electrical switching apparatus and, more particularly, to charging assemblies for electrical switching apparatus. The disclosed concept also relates to electrical switching apparatus, such as circuit breakers.
2. Background Information
Electrical switching apparatus, such as circuit breakers, provide protection for electrical systems from electrical fault conditions such as, for example, current overloads, short circuits, abnormal voltage and other fault conditions. Typically, circuit breakers include an operating mechanism, which opens electrical contact assemblies to interrupt the flow of current through the conductors of an electrical system in response to such fault conditions as detected, for example, by a trip unit. The electrical contact assemblies include stationary electrical contacts and corresponding movable electrical contacts that are separable from the stationary electrical contacts.
Among other components, the operating mechanisms of some low and medium voltage circuit breakers, for example, typically include a poleshaft, a trip actuator assembly, a closing assembly and an opening assembly. The trip actuator assembly responds to the trip unit and actuates the operating mechanism. The closing assembly and the opening assembly may have some common elements, which are structured to move the movable electrical contacts between a first, open position, wherein the movable and stationary electrical contacts are separated, and a second, closed position, wherein the movable and stationary electrical contacts are electrically connected. Specifically, the movable electrical contacts are coupled to the poleshaft. Elements of both the closing assembly and the opening assembly, which are also pivotably coupled to the poleshaft, pivot the poleshaft in order to effectuate the closing and opening of the electrical contacts. A charging assembly, which includes a number of stored energy mechanisms, is often employed to facilitate operation of the closing assembly.
As shown, for example, in FIGS. 1A and 1B, some circuit breakers 2 have direct drive stored energy mechanisms such as, for example and without limitation, a number of closing springs 4 (one closing spring 4 is partially shown in simplified form in FIG. 1A). The charging assemblies 6 of such circuit breakers 2 typically include a cam shaft 8 having a number of cams 10,12, and a catchment 14. The catchment 14 in the example of FIGS. 1A and 1B is pivotably coupled to a side plate 16 of the circuit breaker 2. In such devices, the spring assembly, which includes the aforementioned closing spring(s) 4 and a spring casting 18 biased by the spring(s) 4, is charged by action of the cam shaft 8, and is released so the discharged spring 4 directly drives the main toggle links (not shown) of the closing assembly. As the spring 4 discharges, the catchment cam 12, which has been released, continues to rotate in the charging direction (e.g., counterclockwise in the direction of arrow 20 from the perspective of FIG. 1A). If it rotates far enough, it can interfere with the discharge of the spring 4 and prevent the circuit breaker 2 from completely closing. This undesirable condition is generally referred to as cam shaft over rotation. Although the catchment 14 is generally structured to cooperate with the cam(s) 12 to resist such over rotation of the cam shaft 8, it is possible, particularly after extended use, that the impact surface 22 of the catchment 14 and/or the corresponding catchment surface 24 of the catchment cam 12 can become worn or damaged (see, for example, damaged or deformed surfaces 22′,24′ in FIG. 1B), causing the catchment to be less effective.
There is, therefore, room for improvement in charging assemblies, and in electrical switching apparatus, such as circuit breakers, which employ charging assemblies.